Reduction of nitrogen dioxide by propene over acidic mordenites: influence of acid site concentration, formation of by-products and mechanism

The reduction of nitrogen dioxide to nitrogen by propene was studied over a variety of acidic mordenite zeolites differing in their Si : Al ratio and thus, in their concentration of acid sites. The formation of by-products was monitored applying an ion–molecule reaction (IMR) mass spectrometer. It was found that at fixed conditions the yield of nitrogen increases with increasing concentration of acid sites, confirming that acid sites are the active catalytic centres in the reaction. Apart from nitrogen and nitric oxide, acrylonitrile and ammonia are formed as nitrogen containing gas-phase products in the reaction. In separate experiments, it was shown that acrylonitrile is hydrolysed by water over the acidic zeolites to yield ammonia and acrylic acid. When acrylonitrile is used as reducing agent for nitrogen dioxide, formation of nitrogen is strongly enhanced in the presence of water. Water also has a promoting effect on the formation of nitrogen in the reaction between nitrogen dioxide and propene. Acrylonitrile and its product of hydrolysis, ammonia, are considered to be intermediates of nitrogen dioxide reduction to nitrogen by propene over acidic zeolites.     

Selective attention, memory bias, and symptom perception in idiopathic environmental intolerance and somatoform disorders.

Idiopathic environmental intolerance (IEI) refers to a polysymptomatic condition, similar to somatoform disorders. Various processes seem to contribute to its yet unknown etiology. Attention and memory for somatic symptom and IEI-trigger words was compared among participants with IEI (n = 54), somatoform disorders (SFD; n = 44) and control participants (n = 54). Groups did not differ in a dot-probe task. However, in an emotional Stroop task, attention was biased in IEI and SFD groups toward symptom words but not toward IEI-trigger words. Only the IEI group rated trigger words as more unpleasant and more arousing, and participants remembered them better in a recognition task. These implicit and explicit cognitive abnormalities in IEI and SFD may maintain processes of somatosensory amplification. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mass transfer in a bottom blowing cold model converter

In a model converter containing oil and water the volumetric mass transfer of caprylic acid was determined in dependence of the gas flow rate. Several other parameters were varied such as the number and configuration of nozzles, gas velocity, oil viscosity and volume and model size. Partially the results could be described by dimensionless equations. Visual observations of the bath surface with special regard to the wave formation complete the results of the measurements. By knowledge of the drop size spectrum independently determined, the mass transfer coefficient under dispersion conditions could be evaluated. These values were compared with mass transfer coefficients which had been directly measured by the single rising drop technique as well as the bubble stirred interface without dispersion. It seems that turbulence in dispersed systems does not enlarge the mass transfer coefficient.     

An Alternative Method for Establishing Design Parameters for Novel Coalescers

A design method for establishing the critical parameters for general electrostatic coalescers has been developed. The method allows for characterization of emulsion stability as well as the experimental determination of required electrical field parameters, flow rate (whether laminar or turbulent flow) and physical dimensions (via residence time). The method has been tested on model fluid systems as well as stabilized crude samples with varying water phase characterizations. The method can be utilized for design and diagnostic work.     

Wide temperature operation of 40-Gb/s 1550-nm electroabsorption modulated lasers

Electroabsorption modulated lasers (EMLs) exploiting the quantum confined Stark effect need thermoelectric coolers to achieve stable output power levels and dynamic extinction ratios. Temperature-independent operation is reported between 20/spl deg/C and 70/spl deg/C for InGaAlAs-InP-based monolithically integrated 1550-nm EMLs exploiting a shared active area at 40 Gb/s by actively controlling the electroabsorption modulator bias voltage. Dynamic extinction ratios of at least 8 dB and fiber-coupled mean modulated optical power of at least 0.85 mW are obtained over the mentioned temperature range.     

Carboxylates and sulfates of polysaccharides for controlled internal water release during cement hydration

Calcium and aluminium carboxylates and sulfates of polysaccharides form hydrogels. Four Al- and three Ca-salt hydrogels of such polysaccharides, which were found to be stable enough to be mixed into fresh Portland cement pastes of low initial water-to-cement ratio of 0.275, were compared with respect to their water retardation potential using non-destructively operating low-field ¹H NMR relaxometry. All of the investigated hydrogels release their water to the cement mainly during the accelerated period of cement hydration. At a degree of hydration of about 0.7 the water in the hydrogels is consumed completely by the hydration reactions. Based on Powers’ hydration model the development of the volumetric phase distribution of the investigated hydrating cement with internal curing by the hydrogels was quantified. Within the hardening cement the Ca-salt hydrogels are more stable than the Al-hydrogels which is concluded from the changes of the T₂ relaxation times during the cement hydration.     

An empirical analysis of open source software developers’ motivations and continuance intentions

We investigated open source software (OSS) developers’ intentions to continue their involvement in future projects. The research goal was to analyze the motivations of OSS developers systematically and identify those factors that influenced their continuation. A work motivation model for OSS developers was proposed and a research model was empirically validated using data from a field survey of 148 OSS participants. The results showed that OSS developers’ feelings of satisfaction and their intentions to continue with OSS development was influenced by both helping behavior and economic incentives and also that adequate motivators existed, though OSS developers did not benefit equally and there was substantial room to improve their experiences as OSS developers.     

Microfabrication of single-use plastic microfluidic devices for high-throughput screening and DNA analysis

 Modern drug discovery and genomic analysis depend on rapid analysis of large numbers of samples in parallel. The applicability of microfluidic devices in this field needs low cost devices, which can be fabricated in mass production. In close collaboration, Greiner Bio-One and Forschungszentrum Karlsruhe have developed a single-use plastic microfluidic capillary electrophoresis (CE) array in the standardized microplate footprint. Feasibility studies have shown that hot embossing with a mechanical micromachined molding tool is the appropriate technology for low cost mass fabrication. A subsequent sealing of the microchannels allows sub-microliter sample volumes in 96-channel multiplexed microstructures. Received: 16 May 2001 / Accepted: 3 July 2001     

A real-time navigator for the Visible Human

Adapting data transfer to network throughput enables real-time interactive Web-based navigation of large 3D anatomical data sets. This article focuses mainly on network performance and data encoding issues. We describe our implementation and the principles of slice and label extraction. Evaluating the proposed solution's performance and the server's behavior when serving multiple clients simultaneously points to several issues for further exploration